The use of objects that can be traded for food, candy, treats, or special privileges, with the purpose of reinforcing behavior, is called participant modeling technique contingency contract group extinction procedure token economy

The answer is called a token economy. In addition, a token economy is a method of behavior modification intended to increase needed behavior and decrease unwanted behavior with the use of tokens. The individuals receive tokens directly after exhibiting desirable behavior. The tokens are collected and later replaced by a significant object or privilege.